A student is investigating ultraviolet (UV) radiation and visible light. The student states: 'UV radiation and visible light are both part of the electromagnetic spectrum, so they must interact with the human body in the same way and pose the same health risks.' Explain why the student's statement is incorrect, referring to the properties of UV radiation and visible light.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
UV radiation and visible light are neighbouring regions of the electromagnetic spectrum. Both are produced by the Sun and reach the Earth's surface.
Model answer (5 marks)
UV radiation has a higher frequency than visible light.
Higher frequency means each UV photon carries more energy than a visible‑light photon.
Because of this greater energy, UV can break chemical bonds in skin and eye tissues, causing damage to surface cells and the eyes.
Visible light photons do not have enough energy to break these bonds, so they do not cause the same cellular damage.
Thus different parts of the electromagnetic spectrum interact differently with the body, so the student’s statement is incorrect.
Higher frequency means each UV photon carries more energy than a visible‑light photon.
Because of this greater energy, UV can break chemical bonds in skin and eye tissues, causing damage to surface cells and the eyes.
Visible light photons do not have enough energy to break these bonds, so they do not cause the same cellular damage.
Thus different parts of the electromagnetic spectrum interact differently with the body, so the student’s statement is incorrect.
Examiner tips
- State the frequency difference first, then link to photon energy, then explain biological effect, finally summarise the difference in interaction.
Common mistakes
- Confusing wavelength with energy, or saying visible light is harmless without mentioning photon energy; failing to mention the specific damage to skin/eyes caused by UV.
Mark scheme (5 marks)
- UV radiation has a higher frequency than visible light
- Higher frequency means UV carries more energy (per photon / wave)
- UV radiation can cause damage to surface cells and/or eyes
- Visible light does not carry enough energy to damage cells / does not cause the same harm
- Different parts of the electromagnetic spectrum interact differently with materials/the body, so the student is wrong to say they behave the same way
Key terms in this question
ultraviolet · electromagnetic spectrum
Related
- All Edexcel A-Level Physics (9PH0) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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